I highly recommend visiting the help center and using the keyword test or tester and clicking the questions that you have. I would also make sure to read the testing guidelines, community guidelines, and content guidelines
When posting tester calls I would add the due date, when you’ll be picking testers, if a specific yarn/yarn color is needed and any other requirements you may have for testers
When you post a tester call I believe Ribblr has three steps it mentions to follow with the last being to message testers, I believe there should be a button or something to message testers once you approve them
Good luck and happy crafting! Feel free to ask any more questions or if you need more clarification on anything I said 